It is common practice to line the inner surface of container closures with a moderately compressible material, such as a polymeric material, pulp board, or a multilayer laminated combination thereof. When a closure, containing the liner material, is secured to the finish of a container, such as by applying a torque force to a threaded closure that is engaged with a threaded container finish, the resulting pressure of the closure on the liner, which is interposed between the closure and the container finish, produces a substantially liquid and/or gas-tight seal. When the closure is removed from the container, the liner remains within the closure. Re-engaging the closure with the container finish re-establishes the seal. Liner materials can utilize a pulp or paper substrate or polymeric materials, such as polyolefin foams or laminated multilayer lining materials comprising a combination of pulp or a polymeric foam along with a polymeric film.
In a typical application, closures for containers are lined with a laminated material having a layer of pulp mounted to a layer of aluminum foil by an intermediate wax layer. Such laminated materials also frequently contain a layer of polymer, such as a polyester film, fixed by an adhesive to the foil, and a layer of sealing material fixed by an adhesive to the polyester film. The laminate is produced and shipped as a roll of the sheet material. The roll is slit to the width required by the customer, a container seals are then die cut from the slit roll and then in a closure.
In use, the resulting lined closure is torqued onto a container, such as a bottle or jar, which has been filled with a fluid or solid product. Next, the capped container is passed through a high frequency induction heating unit. During induction heating, the aluminum foil is heated to a temperature in excess of about 65° C., generally about 150° C. or greater, which melts the wax in the layer between the pulp and aluminum foil. The melted wax is absorbed by the pulp, causing the pulp to separate from the remainder of the material. The sealing material (also sometimes referred to as an “innerseal”) typically is selected to match the material of construction of the container, and is heat welded or sealed to the rim of the container (i.e., the container finish) during induction heating process. When a consumer removes the closure from the container, the pulp layer remains in the closure as a liner, leaving the foil, polymer film, and sealing material on the container as a seal to prevent leakage and contamination of the container contents during storage and shipment, and/or to provide evidence of tampering.
An integrated liner and innerseal combination is disclosed in Yousif U.S. Pat. No. 4,596,338. The integrated liner and innerseal combination disclosed in that patent provides an air-permeable paper seal to overcome problems associated with pressure changes within the container due to changes in temperature. Another liner/innerseal combination is disclosed in Cain U.S. Pat. No. 5,712,042, which also discloses a paper layer as the innerseal.
U.S. Pat. No. 6,082,566 to Yousif et al. describes an integrated liner and innerseal combination comprising a transparent innerseal temporarily bound to a chemically resistant liner by a layer of wax. The liner includes a support material such as a layer of cellulose pulp, a chemically resistant polymer layer, an aluminum foil layer between the support and the polymer layer. A synthetic fabric layer, such as spunbonded high density polyethylene, is adhesively secured to the chemically resistant polymer layer. A layer of wax binds the synthetic fabric layer to a layer of heat-sealable polymer. When a disk of the material is placed in a container closure (support layer first) and the closure is secured to the finish of a container, the sealed container can be run through an induction sealing unit to heat the aluminum foil, causing the heat-sealable polymer to bind to the container finish and also causing the wax to melt. When the wax melts, it is absorbed by the synthetic fabric, thus separating the liner from the innerseal, so that upon removal of the closure, the liner remains in the closure and a transparent innerseal (e.g., the heat-sealable film) remains secured over the finish of the container. Such integrated liner and innerseal combinations provide a clear, transparent innerseal, in which the absorbent synthetic fabric layer remains in the liner. Variations on this design in which the synthetic fabric layer is replaced by a layer of paper are also known.
U.S. Pat. No. 6,161,754 describes an integrated liner and innerseal material in which a wax absorbent layer is a synthetic fabric laminated to the lower surface of a liner and having an aluminum foil layer as part of the innerseal portion. These materials provide an opaque innerseal, which prevents the contents of the container from being viewed when an opaque container is utilized.
There is an ongoing need for improved container sealing materials having a clear, transparent seal so that the contents of the container can be viewed through the innerseal, particularly when an opaque container is used. In some applications, it is also desirable to have a liner with a non-absorbent surface in direct contact with the contents of the container, rather than an absorbent fabric or paper layer. Such applications include, for example, when the contents of the container includes volatile materials or liquid substances that can be absorbed by the fabric or paper.
Modern packaging and advertizing often makes use of promotional materials, such as coupons, sweepstakes, games, and the like, to promote products, services, political or social causes, and the like. In many cases, this requires placing the coupon or other promotional material on the exterior of the container, where it is easily removed by individuals who did not purchase the product. This has led some to place coupons inside the product container. When the product is a food or drug item, any coupon that contacts the contents of the container must be printed with an FDA approved ink, or must be sealed in a hermetic pouch, both of which add to the expense of the promotional materials. It would be very useful to be able to place a readily retrievable coupon or other promotional material within a container closure. Some specialized closures have been developed, which have chambers for sealing promotional materials inside the closure itself, however, such specialized closures are expensive and can be complicated to manufacture. Accordingly, there is an ongoing need for ways to conveniently include promotional materials, such as a coupon, within a container closure. There is also an ongoing need for improved container sealing materials that provide functional features such as tamper evidence, preservation of product quality, packaging integrity, and the like.
The present invention provides promotional materials integrated with a container seal, so that the promotional material (i.e., a promotional token) can be included within the container closure and not in contact with the contents of the container. While container seals are a regulatory requirement for many food and drug applications, the container seals of the present invention turn this regulatory requirement into a marketing asset by integrating useful promotional materials into the container seal. The container sealing materials of the present invention can be used with standard, conventional closures to provide promotional materials such as coupons within the closure, without need for expensive, specialty closures with sealed chambers.